Bright nickel plating process



United States Patent 3,352,766 BRIGHT NICKEL PLATING PROCESS Frank Passal, Detroit, Mich., assignor to M&T Chemicals Inc New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 21, 1964, Ser. No. 420,132 11 Claims. (Cl. 204--49) This application is a continuation-in-part of Ser. No. 365,195, filed May 5, 1964, now abandoned.

This invention relates to electroplating nickel and more particularly to the electrodeposi'tion of bright nickel.

Nickel electrodeposits as plated from Watts, high chloride, fluoborate, etc. type baths are not bright when plated in thicknesses substantially greater than those of very thin strike or flash coatings. Such deposits do not increase in luster with increasing thickness but rather decrease in brightness until dull matte deposits are obtained. To obtain thick bright deposits from such baths, it is necessary to add certain additives, commonly of organic nature, which assist in producing highly lustrous deposits with good rate of brightening, It is a common characteristic of such so-called bright nickel plating baths that the deposits tend to increase in luster With increasing thickness. A particular advantage of these bright nickel baths is that bright deposits can be obtained on basis metals which have not been polished or which do not have a high starting luster, within reasonable specification thicknesses of nickel. Other concomitant advantages such as leveling or the ability of the deposits to fill in pores, scratches, or other superficial defects of the basis metal, may also be obtained.

Addition agents useful as brighteners in nickel plating baths are generally divided into two classes on the basis of their predominant function. Primary brighteners are materials used in very low or relatively low concentration, typically 0.002-02 g./l., which by themselves may or may not produce visible brightening action. Those primary brighteners which may exhibit some brightening effects when used alone generally also produce deleterious side effects such as reduced cathode efliciency, poor deposit color, deposit brittleness and exfoliation, verynarrow bright plate range, or failure to plate at. all on low current density areas. Secondary brighteners are materials Which are ordinarily used in combination with primary brighteners but in appreciably higher concentration than that of the primary brighteners, typically 1 g./1. to 30 g./l. These materials, by themselves, may produce some brightening or grain-refining effects, but the deposits are not usually mirror bright and the rate of brightening is usually inadequate.

Ideally, when primary and secondary brighteners of properly chosen and compatible nature are combined it is possible to obtain, over a wide current density range, ductile, leveled deposits which exhibit a good rate of brightening. The rate of brightening and leveling may vary in degree depending on the particular cooperative additives chosen and their actual and relative concentrations. A high degree of rate of brightening and leveling is gen- 4 erally desirable, particularly where maximum luster is desired with minimum nickel thicknesses. The concentrations of the secondary brighteners may usually vary within fairly wide limits. The concentrations of the primary brightener which can be used over a wide range of concentration is of great value in bright nickel plating.

It is an object of this invention to provide improved nickel plate by use of a new class of superior primary brighteners. It is a further object of this invention to provide an efficient process for electrodepositing bright and smooth nickel deposits. Another object of this invention is to provide bath compositions for nickel plating from which bright nickel electrodeposits are obtained. Other objects of this invention may be apparent to those skilled in the art on inspection of the following description.

In accordance with certain of its aspects, the process of this invention comprises electrodepositing nickel from an aqueous nickel electroplating bath containing a secondary brightener and, as a primary brightener, a compound having a cation of the structure wherein R is an alkyl group, R is a hydroxyalkyl group, a is an integer 0-5, I) is an integer 0-4, when a is 0-1, b is 1-4, and a plus I) is less than 6.

R may be an alkyl group including methyl, ethyl, propyl n-propyl, n-butyl, i-butyl, t-butyl, n-amyl, n-hexyl, n-octyl, Z-ethylhexyl, etc. Preferably R may be a lower alkyl, i.e. an alkyl group having l-6 carbon atoms. R may be a hydroxyalkyl group including hydroxymethyl, fi-hydroxyethyl, -hydroxypropyl, fi-dihydroxypropyl, ,B-Z-dihydr-oxypropyl, hydroxy butyls, hydroxy amyls, etc. Preferably R may be a monohydroxyalkyl having 1-6 carbon atoms. 1

Typical compounds of this class which may be effective as primary brighteners are the following:

TABLE I (A) 2,6-dimethyl, N-propargyl pyridinium bromide,

(B) 3,5-dimethyl, N-propargyl pyridinium bromide,

(C) 2,4-dimethyl, N-propargyl pyridinium bromide,

(D) 3,4-dimethyl, N-propargyl pyridinium bromide,

(E) 2,5-dimethyl, N-propargyl pyridinium bromide,

(F) 3-ethyl, 4-methyl, N-propargyl pyridinium bromide,

(G) 2,4,6-trimethyl, N-propargyl pyridinium bromide,

(H) Z-B-hydroxyethyl, N-propargyl pyridinium bromide,

(I) Z-gamma-hydroxypropyl, N-propargyl pyridinium bromide,

(I 3-hydroxymethyl, N-propargyl pyridinium bromide,

(K) 2-methyl, G-gamma-hydroxypropyl, N-propargyl pyridinium bromide,

(L) 2-ethyl, 4,6-di-B-hydroxyethyl, N-propargyl pyridinium bromide,

(M) 2,4,6-tri-hydroxymethyl, N-propargyl pyridinium bromide.

The novel class of primary brighteners of this invention when used in combination with (a) suitable secondary brighteners or (b) secondary and secondary auxiliary brighteners, may give brilliant, nickel deposits which have excellent ductility, good low current density coverage and luster, good rate of brightening, and good leveling characteristics. It is a particular feature of this invention that the preferred novel primary brighteners may be used over a wide range of concentration with attainment of good low current density coverage and ductility of the deposits. 7

Another outstanding advantage is that these novel primary brighteners can withstand long electrolysis without build-up in the nickel plating bath of harmful decomposition products. Prior art nickel plating techniques may include'the use of a number of acetylenically quaternized nitrogen heterocyclic compounds as primary brighteners; but they either produce inadequately lustrous deposits or are difficult to synthesize in high purity and yield; they have limited compatibility with the more commonly used additives. The compounds of this invention do not have these defects and in addition exhibit low rates of consumption.

The primary brighteners. of this invention may be used in concentrations of 0.005 g./l. to 0.10 g./l., the particular concentration chosen depending on the particular types and concentration of secondary and secondary auxiliary brighteners used, and also on such factors as the concentrations of nickel sulfate, nickel chloride, and boric acid; operating conditions, with respect to temperature and degree of agitation; degree of luster, rate of brightening and leveling desired; and the finish of the basis metal, It is preferred to use between 0.01 g./l. and 0.05 g./l.

Secondary brighteners (typically present in amount of l g./l. to 75 g./l., and preferably 1 g./l. to 20 g./l.) which are useful in combination with the primary brighteners, are generally aromatic sulfonates, sulfonamides, or sulfimides which may include such substituted aromatic compounds as 1,3,6-naphthalene trisulfonate, sodium or potassium salts of saccharin, sodium or potassium salts of ortho-sulfobenzaldehyde, benzene sulfonamide, benzene monosulfonate, etc. For use in high chloride type nickel plating baths, a preferred secondary brightener may be a sodium or potassium salt of sulfonated dibenzothiophene dioxide, prepared by sulfonating diphenyl with fuming sulfuric acid (20% oleum). for

about 2. hours, isolating the reaction product and neutralizing. The predominant reaction product is believed to be the compound containing three sulfonic acid groups,

together with some monoand di-substituted components.

pene-l-sulfonate; sodium-3-chloro 2 butene-l-sulfonate; mixed isomer of sodiurn-2-butene-2-hydroxy-l-sulfonate and sodium-2-butene-1-hydroxy-2-sulfonate, prepared by reacting butadiene monoxide with sodium sulfite; or phenyl propiolamide may be used in conjunction with the secondary brightener or brighteners.

All of the compounds of this invention will give bn'lliant, highly leveled deposits particularly when used in combination with. secondary and auxiliary secondary brighteners. Some of the compounds of this invention give optimum results with relatively low (i.e. below about 0.05 g./l.) concentrations of anionic wetting agents (such as sodium lauryl sulfate, sodium lauryl ether sulfate, sodium di-n-hexyl sulfosuccinate). These compounds must then be used in the absence of wetting agents or in the presence of substantially lower amounts than normally used and with mild agitation of the solution or of the part being plated. Several of the compounds of this invention are highly compatible with normally used anionic wetting agents and over a wide concentration range of the latter. With these compatible brighteners, outstanding examples of which are 2,4,6-trimethyl, N-propargyl pyridinium bromide and 2,4-dimethyl, N-propargyl pyridinium bromide, the degree of agitation may vary from very mild to very strong.

Conventional baths and processes for electroplating bright nickel are described in Principles of Electroplating and Electroforming, Blum and Hogaboom, pp. 362- 381, revised third edition, 1949, McGraw-Hill Book Co., Inc., New York; and in Modern Electroplating, edited by A. G. Gray, The Electrochemical Society, 1953, pp. 299-3 55. The control and operating conditions, including the concentration of the bath ingredients, pH, temperature, cathode, current density, etc., of these conventional baths are generally applicable to the present invention. Practically all baths for electroplating bright nickel con: tain nickel sulfate; 2. chloride, usually nickel chloride; a buffering agent, usually boric acid; and a wetting agent. Such baths include the Well-known Watts bath and the high chloride bath. .Other baths may contain, as the source of the nickel, a combination of nickel fiuoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride, or a combination of nickel sulfamate and nickel chloride. Typical Watts-type baths and high chloride baths are noted in Tables II and HI.

TABLE II Watts-type baths:

Nickel sulfate 200 g./l. to 400 g./l. Nickel chloride 30 g./l. to 75 g./l. Boric acid 30 g./l. to 50 g./l. Temperature 38 C. to 65 C. Agitation Mechanical and/ or air or solution pumping, etc. pH 2.5 to 4.5 electrometric.

TABLE III High chloride baths:

Nickel chloride g./l. to 300 g./l. Nickel sulfate 40 g./l. to 150 g./l. Boric acid 30 g./l. to 50 g./l. Temperature 38 C. to 65 C. Agitation Mechanical and/or air or solution pumping. pH 2.5 to 4.5 electrometrie.

Best plating results are usually achieved in the electrodeposition process when there is used a method of preventing the thin film immediately adjacent to the cathode from becoming depleted in cation content. This is desirably ac complished by agitation, such as by air agitation, solution pumping, moving cathode rod, etc.

For the purpose of giving those skilled in the art a better understanding of the invention, illustrative examples are given. In each of the examples, an aqueous acidic nickelcontaining bath was made up with the specified components. Electrodeposition of nickel was carried out by passing electric current through an electric circuit comprising a nickel anode and a sheet metal cathode, both immersed in the bath. The baths were agitated, usually by a moving cathode. Bright electrodeposits were ob tained in all the tests included herein as examples.

In Examples 1 through 18 inclusive, the following standard bath was used as a 'base solution:

g./l. Nickel sulfate 300 Nickel chloride 60 Boric acid 45 The primary brighteners are identified from Table I, supra. The secondary brighteners which are used in the following examplesas noted in Table IV infra, include:

TABLE IV Secondary brighteners (N) O-benzoic sulfimide (Na salt),

(0) Dibenzene sulfonamide,

(P) N,N'-bis(phenylsulfonyl) 4,4 diphenyl disulfonamide,

(Q) Sulfonated dibenzothiophene dioxide.

The auxiliary secondary brighteners which are used in the following examples as noted in Table V infra, include:

TABLE V Auxiliary secondary brighteners (R) Sodium-3-chloro-2-butene-l-sulfonate, (S) Sodium allyl sulfonate.

The wetting agents which are used in the following examples as noted in Table VI infra, include:

Temp., C.

CD asd TABLE VIII In examples 19-26 inclusive, the following standard bath was used as a base solution:

Nickel chloride 250 5 Nickel sulfate Boric acid TABLE VI Wetting agents (T) Sodium lauryl sulfate, (U) Sodium di-n-hexyl sulfosuccinate.

In the following examples asd signified amperes per square decimeter.

The foregoing examples illustrate specific baths and processes. It is understood that the compositions and conditions may be varied. Although the potassium and sodium salts were most often used and are preferred, they may be partially or completely replaced by such other salts as The nickel electrodeposits obtained from baths utilizin that mirror-bright lustrous electrodeposits having a high degree of ductility are obtained over a wide range of cathode current densities. The bright nickel electrodeposits are preferably plated on a copper or copper alloy basis metal. However, they may be electrodeposited di- The novel primary brighteners of this invention may wherein R is an alkyl group, R is a hydroxyalkyl group, a is an integer 05, b is an integer 04, when a is 01, b is 14, a plus b is less than 6, and X' iS an inert water- Thus for example the charge heterocyclic compound 7 2,5-dimethyl pyridine,

S u 0 6 g m n w d a e r a n c O m n m 0 2 2 0 02 2 0 04 3 0 0 45 0 0 2 2 0 02 3 0 02 3 0 aaao m M m 5 m m H a m e. 0 n g .C H .w m c o m H o m A S I .H W m u b .l k t e 1 l b 3 r. .m 6 m m cm m R m e 6 6: N g 6 P u .1 .m .m .m w m .n e m m m d mmmm r A oNRT oNRU oosT oosn GNRT GNRU GosT oosn m b m v. m R w .m Wyyy m d m b R Y PPPP V 1 11111... 0 O u d V.V.V.V. N h u h u a n s m a m h h h h m n a 1D .1 tttt n n n n n N u e o P P e e e e p h e y m m m m m n u n n n u 6 1W r b t :1 '1 '1 '1 a k t P u d 4 n d m n n u n n u .m g m e 1 a 6 5 4 2 m 2 2 2 a n M.. m n .m r b w m 2 3 2 3 0 5 0 5 0 5 0 5 0 5 m m m m m m m m m w w m m m w w m w 07 p m e T 4 4 A: 4 A: 4 4 4 4 A. 4 4 4 5 5 5 5 5 m a D C 0 23 0 0 23 0 0 230 0 2 30 0220 0220 023 0 0 220 0230 0 23.0 0 23 0 0 230 0 220 0 3 33 0 0 23 0 0&30 0 33 0 0 4330 TABLE VII Amount, g /1 Additive ANRT BNRT CNRT DNR ENRT.FN RT GNRT HNRT TNRT JNRT KNRT LNRT MNRT GoRU GPsU GQsU GORU oPsU Typical reactants HCECCH2X which may be employed include those wherein X may be an inert watersoluble, bath-compatible anion preferably halogen. Most preferred because of ease of reaction and availability may be propargyl bromide, HCECC H Br.

It will be apparent to those skilled in the art that inertly substituted reactants may be employed.

The reaction of the heterocyolic compound and the acetylenic halide may typically be effected under mild con- .ditions, preferably in the presence of solvent. The reaction may occur readily in high yield typically at room temperature'with slight warming usually occurring at the a beginning of the reaction. The product generally may be a well-defined crystalline solid which may be recovered from the reaction system as by filtration followed by washing with appropriate solvent such as acetone. Recrystallization is generally unnecessary and the product may be to other novel compounds in practice of this invention may be effected by the reaction thereof with -e.g. soluble silver salts ofdesired anions such as acetate, sulfate, perchlorate, methosu-l'fate, "etc. Typically this reaction may be effected in aqueous medium by "mixing equivalent amounts of the reactants "and filtering elf the insoluble silver halide,

R R p i AgBr I -amazon.

ooooHr Preparation of the novel compounds of this invention may be further illustrated =by-1ihe following illustrative specific Examples 24-28':

Example 24.-Synthesis of 2,4,6-trimet'hyl, N-propargyl pyridinium bromide- 10 grams of 2,4,6-trimethyl pyridine, 20 ml. of propargyl bromide, and 25 ml. of dime'thylformamide were allowed to stand for hours at room'temperature and 25 ml. of acetone were then added. After 5 days a crystalline-precipitate was obtained which was filtered 01f, washed with acetone and air-dried. Weight product 14.1 grams (70% yield). M.P. 198-199 C. (Fisher-Johns Apparatus).

Example 25.Synthesis of 3,5-dz'methyl, .Nepropw'gyl pyridinium bromide 10 grams of 3,5-dirnethyl pyridine, 20 ml. of propargyl bromide, and 25 ml. of dimethylformamide were allowed to stand for 16 hours at room temperature and 25 ml. of acetone were then added. The crystalline precipitate was filtered off, washed with acetone and air-dried. Weight product 16.0 grams (76% yield.) M.P. ,198199 C. (F isherJ ohns) Example 26.Synthesis 09" Z-gamma-hydroxypropyl, N-

propargyl pyridinium bromide 10 grams of Z-gamma-hydroxypropyl pyridine, 20 ml. of propargyl bromide, and 25 ml. of dimethylformamide were allowed to stand at room temperature for 16/2 hours and 25 ml. of acetone were then added. The crystalline precipitatewas filtered off, washed with acetone and airdried. Weight product 16.7 grams of (94% yield). M.P. 137138 C. (Fisher-Johns).

Example 27.Synthesis of 2,4-dimethyl, N-prapargyl pyridinium bromide 10 grams of 2,4-dimethy'l pyridine, 20 ml..of propargyl bromide, and 25 ml. of dimethylformamide were allowed to stand for, 48 hours at room temperature and 25 ml. of acetone were then added. The crystalline precipitate was filtered oil and air-dried. Weight product 18.0 grams yield). M.P.146-147" C. Fisher-Johns).

Example 28.-Synthesis 07 3'-ethyl, 4-m'etl1y'l, N-propargyl pyridinium bromide 10 grams of B-ethyl, 4-.methyl pyridine, 20 ml. of propargyl bromide, and 25 ml. of dimethylformamide were allowed to stand for 48 hours at room temperature and 25 ml. acetone were then added. The crystalline precipitate was filtered off, washed with acetone and air-dried. Weight product 12.2 grams .(6-l% yield). M.P. 146 C. (Fisher-Johns).

Although this invention has been illustrated by reference to specific examples, numerous changes and modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled-in-the-art.

I claim:

1. The process for electrodepo'siting nickel which comprises electrodepositing nickel from an aqueous acidic nickel electroplating bath containing a secondary bright- :ener and, as a primary brightener, an effective amount of a compound having a cation of the structure Mmcmczon wherein R is an alkyl group, R is a hydroxy alkyl group, a is an integer 0-5, b is an integer 0-4, when a is 0-1, b is 1-4, and a plus b is less than 6.

2. The process claimed in claim 1 wherein said primary 'bn'ghtener is present in amount of 0.005 g./l. .to (L10 vgz/l.

3. The process claimed in claim 1 wherein said compound is 2,6-dimethyl, N-propargyl pyridinium bromide.

4. The process claimed in claim 1 wherein said compound is 2,4,6-trimethyl, N-propargyl pyridinium bromide.

5. The process claimed in claim 1 wherein said compound is 2,4-dimethyl, N-propargyl pyridinium bromide.

6. The process claimed in claim 1 wherein said com.- pound is 2,5-dimethyl, N-propargyl pyridiniumbromide.

7. An aqueous acidic electrolytic bath containing soluble salts for the electrodepos'iti'on of nickel andcontaining as a primary brightener, an eifective amount of a compound having a cation of the structure E LCHFCEOH wherein R is an alkyl group, R is a hydroxy alkyl group, a is an integer 0-5, b is an integer 04, when a is 01, b is 14, and a plus b is less than 6.

8. An aqueous electrolytic bath containing soluble salts for the electrodeposition of nickel as claimed in claim 7 wherein said primary brightener is present in amount of 0.005 g./l. to 0.10 g./l.

9. An aqueous electrolytic bath containing soluble salts for the electrodeposition of nickel as claimed in claim 7 wherein said primary brightener is 2,6-dimethyl, N-propargyl pyridinium bromide.

10. An aqueous electrolytic bath containing soluble 10 claim 7 wherein said primary brightener is 2,4,6-trimethyl, N-propargyl pyridinium bromide.

11. An aqueous electrolytic bath containing soluble salts for the electrodeposition of nickel as claimed in claim 7 wherein said primary brightener is 2,4-dimethyl, N-propargyl pyridinium bromide.

References Cited UNITED STATES PATENTS 2,644,789 7/ 1953 Schenk 204-49 3,006,822 10/1961 Todt 204-49 3,054,733 9/ 1962 Heiling 204-49 3,170,853 2/1965 Kroll 204-49 3,218,244 11/1965 Passal et a1 204-49 3,255,096 7/1966 Towle et al 204-49 3,261,840 7/1966 Kroll 204-49 X JOHN H. MACK, Primary Examiner.

salts for the electrodeposition of nickel as claimed in 20 G. KAPLAN, Assistant Examiner. 

1. THE PROCESS FOR ELECTRODEPOSTITING NICKEL WHICH COMPRISES ELECTRODEPOSITING NICKEL FROM AN AQUEOUS ACIDIC NICKEL ELECTROPLATING BATH CONTAINING A SECONDARY BRIGHTENER AND, AS A PRIMARY BRIGHTENER, AN EFFECTIVE AMOUNT OF A COMPOUND HAVING CATION OF THE STRUCTURE 1-(HC*C-CH2-),R(A),R''(B)-PYRIDINIUM WHEREIN R IS AN ALKYL GROUPS, R'' IS A HYDROXY ALKYL GROUP, A IS AN INTEGER 0-5, B IS AN INTEGER 0-4, WHEN A IS 0-1, B IS 1-4, AND A PLUS B IS LESS THAN
 6. 